System for the production of cast concrete members



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SYSTEM FOR THE rnonuc'rxou 0F CAST CONCRETE MEMBERS Filed Dec. 5. 196' 8 Sheets-Sheet 1 FIG. 2.

INVENTOR 3 WILLIAM E. MITCHELL ATTORNEYS Aug. 11, 1970 w. MITCHELL SYSTEM FOR THE PRODUCTION OF CAST CONCRETE MEMBERS 8 Sheets-Sheet 2 Filed Dec. 5.

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SYSTEM FOR THE PRODUCTION OF CAST CONCRETE MEMBERS 8 Sheets-Sheet 4 Filed Dec. 5, 196

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8 Sheets-Sheet 5 am mu INVENTOR I ATTORNEYS WILLLAM E.M1TCHELL SYSTEM FOR THE PRODUCTION OF CAST CONCRETE MEMBERS Aug. 11, 1970 Filed Dec Aug ll, 1970 w. E. MITCHELL SYSTEM FOR THE PRODUCTION OF CAST CONCRETE MEMBERS 8 Sheets-Sheet 6 Filed Dec. 5, 196

11 QWN INVENTOR WILLIAM E. MITCHELL my ATTORNE Aug ll, 1970' w. E. MITCHELL 2 SYSTEM FOR THE PRODUCTION OF CAST CONCRETE MEMBERS Filed Dec. 5, 196' s Sheets-Sheet a I INVENTOR g: WILLIAM E .MITCHELL ATTORNEY United States Patent Tenn., assignor toenn., a corporation 15 Claims ABSTRACT OF THE DISCLOSURE A system for producing cast concrete members wherein a manufacturing area housing the sequentially used items of production equipment is locatedcentrally between an elongated curing area and a similarly elongated unloading-overrun area, and a casting bed moves back and forth several times during each production cycle while the various operations of the manufacturing process are performed. The casting bed comprises a lengthy stress frame which is mounted on a track extending the full length of the facility and carries a molding form on which the concrete member is cast by, equipment which normally remains stationary in the manufacturing area while the bed moves beneath it. The casting bed is moved along the track at any desired speed in either direction by suitable driving means, such as two sets ofselectively operable hydraulic motors which are located on opposite sides of the manufacturing area and drive rubber-tired wheels having frictional engagement with the stress frame.

BACKGROUND OF THE INVENTION This invention relates to the manufacture of cast concrete structural members, hereinafter sometimes referred to as concrete planks in the interest of brevity, and is more particularly concerned with an improved system for producing such planks more efficiently and at less cost than has been possible by utilization of apparatus heretofore available.

Prior to the present invention, a number of different types of equipment were devised for making concrete structural members by a substantially'continuous process, such as those disclosed in Pat. Nos. 3,055,073 and 3,177,552. Pat. No. 3,055,073 shows an apparatus for the production of solid prestressed concrete members utilizing a continuously moving mold consisting of an endless bottom belt and'a pair of endless side belts, while the machine of Pat. No. 3,177,552 produces a hollow or cored reinforced plank by means of' an assembly of concrete feeding silos and core members which move continuously over the surface on which the'p'lank is cast while the core members also reciprocate longitudinally relative to the silos. Another'prior apparatus for producing cored concrete planks is shown in Pat. No. 3,217,375 wherein the soffit of the plank is first formed on a stationary casting bed by means of hopper and roller units which travel the length of the bed, after which the remainder of the plank, including the cored openings therein, is produced by a casting machine which alsomoves along the bed. The completed plank is then cured andsubsequently cut into desired lengths while remaining stationary on the bed.

Although each of these prior devices possesses certain advantages, they are either relatively inefficient or expensive in first cost, operation and maintenance, or objectionable in other respects; 1

SUMMARY OF THE INVENTION The present invention resides in a system for manufacturing castconcrete planks which is basically a simplification of, and an improvement on, the apparatus of Pat. No. 3,217,375. Although the specific embodimentof the invention disclosed herein is adapted to produce hollow orco'jred prestressed concrete planks of the type shown in Pat-No. 3,217,375, it should be understood that the invention concept is also applicable to the manufacture of various other forms of concrete structural members, and that the term structural member" as used herein is not limited to load-bearing members, but also includes such other precast concrete elements as wall panels, partitions, column covers and the like.

The system of the present invention is characterized by the inclusion of a main manufacturing building of suitable size to accommodate substantially all of the production equipment, a curing area and an unloading-overrun area positioned on opposite sides of, and each of much greater length than, the main building, a fixed track extending the full' length of the curing area, main building and unloading-overrun area, and a casting bed which moves back and forth along the track several times during each pro: duction cycle while the various manufacturing operations are performed.

The curing area may comprise a kiln of inexpensive, Quonset type construction, and may be provided with curtains of insulating and vapor-proof material which can bereadily lowered around the cast plank to control the curing operation. The casting bed comprises a stress frame of a length slightly less than that of the curing area which carries prestressing jacking heads and a molding form is of sufficient strength to withstand the forces incident to prestressing, and is supported on the track in any suitable manner, as by a number of closely spaced rollers. The upper surface of the stress frame is provided with a pair of rails on which the casting and other producing equipment is adapted to be supported in a normally stationary position in the main building while the casting bed moves beneath it.

Another feature of the invention resides in the provision of two sets of low speed, high torque hydraulic motors, located on opposite sides of, but relatively close to, the main building, which are selectively operable to drive the casting bed along the track in either direction at various speeds through rubber-tired wheels having frictional engagement with the stress frame.

The apparatus of the present invention is an improvement over those of the prior art, particularly as exemplified by Pat. No. 3,217,375, in that it enables the pro duction of concrete planks at less cost, with less personnel, and with a shorter production cycle. By centralizing substantially all of the production equipment in a relatively small main building and utilizing a rolling casting bed, the need for an enclosed and heated building as long as the bed is eliminated, as is the need for movable gantries, concrete delivery devices and other pieces of miscellaneous equipment. The centralized system also aids in reducing the man-hours required to police a fixed bed, permits better supervision of personnel, and controlof the manhfacturing process, and minimizes handling of the product. The construction of the curling kiln provides excellent conditions for controlled curing of the cast plank and enables a reduction in the curing time which, together with the more eflicient use of labor resulting from centrali zation of the manufacturing operations, makes possible a Substantially shorter production cycle than that attainable by use of the systems previously known.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic plan view of a system or facility for producing cast concrete structural members or planks in accordance with the present invention, certain of the elements of the system having been omitted in the interest of simplicity;

FIG. 2 is a fragmentary perspective view of one form of plank which the system of FIG. 1 is adapted to pro- 'duce;

FIG. 3 is an enlarged diagrammatic end view of the system taken from the line 33 in FIG. 1;

FIGS. 4 and 5 are enlarged sectional views of the system taken on the lines 44 and 5-5, respectively, 1n FIG. 1;

FIG. 6 is a plan view of the casting bed with certain parts broken away;

FIG. 7 is a transverse sectional view of the casting bed stress frame, pallet and side forms with certain parts broken away and others omitted in the interest of clarity;

FIG. 8 is a fragmentary side view of the pallet and side form actuating means taken from the line 8-8 in FIG. 7;

FIGS. 9 and 10 are fragmentary sectional views of the storage and transfer portion of the manufacturing area taken on the lines 99 and 1010, respectively, in FIG. 1, omitting the stored equipment;

FIG. 11 is a side view of the transfer car;

FIG. 12 is a plan view of the assembled soffit laying and rolling units, including a showing of the means for holding the various units of manufacturing equipment in operating position;

FIG. 13 is a side view of the assembled soffit laying and rolling units of FIG. 12;

FIG. 14 is a transverse sectional view taken on the line 14-14 in FIG. 12;

FIG. 15 is a side view of the main casting machine; and

FIG. 16 is a schematic view of the hydraulically actuated elements of the system illustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, there is diagrammatically illustrated therein the layout of a system or facility for manufacturing cast concrete planks embodying the preesnt invention which comprises a main manufacturing building 10, of suflicient size to accommodate substantially all of the production equipment, to one end of which (the left-hand end as viewed in FIG. 1) is connected a curing area in the form of a kiln 12 of Quonset type construction having a length much greater than that of main building 10 and suflicient to contain an elongated casting bed indicated generally at 14. At the other end of the main building, opposite the kiln 12, is a crane or unloading bay 16 from the outer or right-hand end of which extends another elongated Quonset type building 18, the bay 16 and building 18 together constituting what may be termed an unloading-overrun area.

Passing centrally through main building 10 and extending the full length of kiln 12, building 10 and the unloading-overrun area 16, 18 is a fixed track 20, consisting of a pair laterally spaced angle iron rails 21, on which the casting bed 14 is adapted to be rolled back and forth from the kiln to the unloading-overrun area, passing through the main building several times during each production cycle. The bed 14 is moved along the track 20 by two driving units indicated generally at 22, 24, located in kiln 12 and overrun building 18, respectively, close to the entrances thereof, and hereinafter described in detail.

In a typical installation embodying a 540 feet long casting bed 14, main building 10 may have a length of approximately 65 feet parallel to track 20 and may extend approximately 40 feet on each side of the track, the curing kiln 12 may have a length of approximately 550 feet, the unloading bay may extend for a distance of approximately 70 feet to the right of building 10, and the overrun building 18 may have a length of approximately 480 feet.

Although, as indicated above, the broad concept of the present invention is applicable to the production of a wide variety of precast concrete members, the facility illustrated in the accompanying drawings is particularly adapted to manufacture cored prestressed concrete planks of the form illustrated in FIG. 2. As there shown, the plank 25 comprises a soffit layer or bottom wall 27, an upper layer or top wall 29, and a plurality of laterally spaced we'bs 31, 33, 35, 37 which interconnect the bottom and to walls, the webs 31 and 37 forming the side walls of the plank while webs 33 and 35 form partitions which divide the interior of the plank into three longitudinally extending core openings 39.

The apparatus herein disclosed may be employed to form planks wherein the bottom and top walls and the webs are all made of the same kind of concrete. However, the production equipment hereinafter described is adapted to manufacture planks wherein the bottom wall 27 is made of a lightweight dry mix of aggregate and cement of a composition similar to that employed in the manufacture of concrete blocks, commonly referred to as dry concrete, while the top wall 29 and webs 31, 33, 35, 37 are made of a relatively dense, structurally strong, wet concrete mix, the bottoms of the webs being securely bonded to the bottom wall in the finished product.

As shown in FIG. 2, the plank 25 includes a plurality of prestressed strands or cables 41, suitable in size, strength and number to provide the desired amount of prestress in the plank, and also incorporates reinforcing members, such as laterally extending rods 43, to meet the strength requirements of the job for which the plank will be used. The prestressing elements 41 are located in and bonded to those portions of the plank which are made of high strength wet concrete, and the reinforcing members 43 are so placed as to tie into the wet concrete, even though portions thereof may pass through the dry concrete bottom wall 27. During casting of the plank, the core openings 39 are filled with a suitable granular core material, such as aggregate or sand, which may be removed after the concrete portions of the plank have been cured. If, however, it is desired that the core material remain in the finished product for insulating or other purposes, it preferably consists of a relatively lightweight, substantially incompressible insulating material, such as vermiculite or perlite.

As indicated in FIGS. 1 and 3, the portion of main building 10 on one side of track 20 (to the right as viewed in FIG. 3) constitutes a batching and material storage area 26 and accommodates a fixed overhead concrete batch plant 28, a concrete mixer 30 and a chute or conveyor 32 for delivering either dry concrete to a point 34 above track 20 at which a soflit laying unit 36 is positioned when in use, or wet concrete to a point 38 at which the concrete hopper of a main casting machine 40 is positioned when in use. Area 26 also accommodates a fixed overhead core material container 42 and a chute 44 for delivering core material to a point 46 above track 20 at which the core material hopper of main casting machine 40 is positioned when in use.

The portion of building 10 on the opposite side of track 20 (to the left as viewed in FIG. 3) constitutes an equipment storage and transfer area 48 housing a plurality of tracks 50 parallel to, but lying in a plane above the plane of, track 20 on which the sofiit laying unit 36 and main casting machine 40 are stored when not in use, along with such other equipment items as a pallet cleaning and oiling unit 52, a soffit rolling unit 54 and a plank cutting unit or saw 56. Extending perpendicularly to storage tracks 50 and intersecting main track 20 is another track 58 on which is mounted a transfer car 60 adapted to move the various equipment units from and to storage tracks 50 to and from normally stationary operating positions above the casting bed 14 as the latter moves along track '20, as hereinafter described. The area between the rails of transfer track 58 opposite the storage tracks 50 closest to track 20 is excavated to provide a cleaning pit 62 having a drain 64, at which location the equipment units may be cleaned after use, before being returned to storage.

Also located in storage and transfer area 48 adjacent track 20 and the right-hand wall of building '10 is a main power unit 66 which provides hydraulic power to the casting bed drive units 22, 24 and other elements of the installation hereinafter described. Positioned on the other side of track 20 opposite main power unit 66 is a control console 68 having suitable connections to power unit 66, drive units 22, 24 and the other elements actuated by the power unit. The console 68 is so arranged that substantially all of the manufacturing operations involved in producing cast concrete planks by means of the apparatus of the present invention can be either directly controlled or supervised by the operator of the console.

Referring now to FIGS. 4-8 in addition to FIGS. 1 and 3, the casting bed 14 comprises a massive elongated stress frame made up of longitudinally extending members 70, cross members 72 and diagonal lbracing members 74 which form a base extending the full length of the casting bed with the cross members 72 projecting outwardly on each side beyond longitudinal members 70. Mounted on the ends of cross members 72 are a pair of longitudinally extending side members 76, in the form of vertically positioned I-beams, on the upper surfaces of which are mounted a pair of angle iron rails 78 extending the full length of the casting bed adapted to support the various units of production equipment previously mentioned while the casting bed is moved beneath the latter. Spring mounted beneath the cross members 72 of the stress frame by means of brackets 80 are a plurality of grooved wheels 82 equipped with roller bearings which support the casting bed on the rails 21 of track 20. The wheels 82 along one side of the casting bed (the left side as viewed in FIGS. 4 and are fixed against lateral movement relative to the bed, while the wheels on the other side are so mounted as to have sufiicient end play to compensate for normal track variations and to reduce binding during travel.

-Within the space between side members 76, the stress frame carries a pallet 84 which is supported above the cross members 72 on longitudinally extending beams 86 having fixed thereto and depending therefrom longitudinally spaced angle irons 87. The bases of angle irons 87 are welded to the stress frame at the longitudinal center point of the frame, but are free to slide longitudinally relative to the frame at all other points in order to allow for expansion and contraction of the pallet due to changes in temperature during curing. The length of the pallet is less than that of the casting bed (for example, with a casting bed 540 feet in length, the pallet is 500 feet long) so as to leave spaces at the ends of the stress frame for the mounting of a pair of jacking heads 88 closely adjacent the ends of the pallet. The remainder of the space at each end of the stress frame beyond the jacking head is provided with an expanded metal walkway 90.

As shown best in FIGS. 7 and 8, the casting bed is also provided with a pair of longitudinally extending side forms 92 which cooperate with pallet 84 to shape the cast plank to the form illustrated in FIG. 2, and are so mounted as to be movable between the substantially vertical, raised positions shown in full lines, and the outwardly inclined, lowered positions shown in broken lines, in FIG. 7. Because of the great length of the casting bed, it is preferable to divide each of the side forms into sections of from to feet in length, and to mount 6 each section individually for pivotal movement about a horizontal axis positioned below and parallel to the adjacent side edge of pallet 84.

It should here be noted that the pallet 84 and side forms 92 represent only one type of casting form presently employed, and that various other casting forms may be used in practicing the invention.

In the structure illustrated, each section of side forms 92 is fixed at its longitudinal mid-point to the upper end of a center actuator cam 94, and at points adjacent its ends to a pair of outside actuator cams 96, all three cams being rigidly mounted on a horizontally extending torque tube 98 which is journaled in a plurality of bushings 100 fixed to and extending outwardly from the adjacent pallet supporting beam 86. Center actuator cam 94 is provided with a tail portion 102 which extends below the pivotal axis of torque tube 98 for connection to hydraulic actuating means extending transversely of the stress frame beneath the pallet 84. As shown in FIG. 7, the actuating means for each pair of side form sections comprises a hydraulic cylinder 104, a piston 106 and an elongated piston rod 108, the tail portion 102 of the center cam at one side of the pallet being pivotally connected to one end of hydraulic cylinder 104 while the center cam on the other side of the pallet has its tail portion pivotally connected to the outer end of piston rod 108.

With this construction, it is evident that the side forms may be automatically moved from their vertical raised positions to their inclined lowered positions after the cast plank has been cured by supplying hydraulic pressure from main power unit 66 to the right-hand ends of all cylinders 104 simultaneously through the connections schematically illustrated in FIG. 16, but omitted from the other figures in the interest of simplicity. It is also obvious that the side forms may be raised to their vertical positions, after the cast plank has been removed from the pallet and the pallet has been cleaned and oiled in preparation for the next casting cycle, by simply reversing the direction of flow of the hydraulic fluid to and from cylinders 104. As will be seen from FIG. 16, all of hydraulic cylinders 104 are connected in parallel by suitable piping 110 carried by the casting bed and terminating at one end of the bed in a pair of quick disconnect couplings 112 adapted to be connected to the ends of lines 114, which carry hydraulic fluid from and to power unit 66, whenever lowering or raising of the side forms is desired. It will be understood that the supply of hydraulic pressure to the side form actuating cylinders 104 may be controlled from the console 68 in any suitable manner, as by means of solenoid operated valve in the power unit.

Referring now to FIG. 4, there is shown therein one of the two drive units by which the casting bed 14 is moved back and forth along track 20 between curing kiln 12 and the unloading-overrun area 16, 18 while the various operations of the production cycle are being performed, the unit illustrated being that located just inside the curing kiln adjacent building 10, and indicated generally at 22 in FIG. 1. It will be understood that the other drive unit 24, located in overrun building 18 adjacent crane bay 16, is of the same construction as that shown in FIG. 4.

Driving units 22, 24 must be capable of moving the casting bed, which weighs approximately 500,000 pounds when fully loaded, along the track 20 in opposite directions at various speeds ranging from 3 to 100 feet per minute, using only one drive unit at a time. Although other drive means may be capable of meeting these variable low speed, high torque requirements, the presently preferred drive system embodies Mark IV Staffa hydraulic motors, manufactured by Chamberlain Industries Limited, of London, England, of the type illustrated in Pat. No. 3,354,786. However, it is also contemplated that the casting bed may be floatingly supported in a water-filled trench, instead of being roller mounted on the rails of a track, in which event the torque requirements would be substantially less and a cable type towing mechanism would suflice for moving the bed back and forth.

By locating the driving units 22, 24 at the positions indicated in FIG. 1, one unit will always be in frictional driving contact with the casting bed. The console operator is thus able to selectively actuate one of the drive units at a time, and to control the speed and direction of movement of the bed by a single manually operated switch or lever at the console 68.

As shown in FIG. 4, each driving unit comprises a pair of variable speed, reversible hydraulic motors 116 of the type above described, located on opposite sides of track and having vertically disposed driving shafts 118 the lower ends of which are connected through couplings 119 to the upper ends of driven shafts 120, on which are mounted rubber-tired wheels 121 having frictional engagement with the side members 76 of the casting bed 14. Each driven shaft is rotatably supported in bearings 122 and 124 located, respectively, above and below the wheel 121, which bearings are fixed to and extend inwardly toward the casting bed from a vertically extending tubular support member 126. The lower end of support member 126 is connected to an inwardly inclined pipe section 128, the lower end of which is so shaped as to rest on the outer surface of a horizontally extending tubular member 130 intermediate the ends thereof. The ends of member 130 are provided with eccentrically disposed pivot shafts 132 which are journaled in bearings 134 adjustably mounted on plates 136 secured to the foundation 138 of track rails 21. Each pair of plates 136 on opposite sides of the track are connected by a tension rod 140.

Mounted on the upper ends of support members 126 are inwardly extending motor mounting plates 142 on which the motors 116 are supported, and which also support a pair of upwardly extending beams 144. The beams 144 in turn support means which move the motor driven wheels 121 into and out of frictional engagement with the side members 76 of the casting bed, and also control the amount of thrust exerted by the wheels against the side members. In the embodiment illustrated, this means comprises a hydraulic cylinder 146 having one end pivotally connected to the upper end of one of beams 144, and a tension rod 148 connected to the piston rod 150 of cylinder 146 by a turnbuckle 152. The opposite end of the tension rod is threaded and passes freely through an opening in a bracket 154 mounted on the upper end of the other beam 144, the outer end of the tension rod beyond the bracket carrying a spring 156 the pressure of which is adjustable by means of nuts 158 threaded onto the extremity of the tension rod. The threaded portion of tension rod 148 inwardly of bracket 154 is provided with a pair of stop nuts 160 so that movement of the tension rod to the left as viewed in FIG. 4 is transmitted to the left-hand beam 144 and support member 126 to move the associated wheel 121 outwardly with respect to the casting bed.

As indicated in FIG. 16, hydraulic pressure fluid may be supplied to either end of cylinder 146 from power unit 66 through suitable piping 162 (not shown in FIG. 4). When the hydraulic pressure is applied to the right-hand end of cylinder 146, the beams 144, support members 126 and pipe sections 128 are moved outwardly away from one another, pivoting on shafts 132, so as to move thhe driving wheels 121 out of engagement with the casting bed side members 76. Stop members 163, fixed to the foundation 138, are provided adjacent pipe sections 128 to limit the outward movement of the motor supporting members. When it is desired to re-engage the driving wheels with the casting bed, the hydraulic pressure is applied to hte left-hand end of cylinder 146 so as to pull the motor supporting assemblies back to their vertical operating positions. The amount of thrust which the driving wheels 121 exert against the casting bed side members 76 is so controlled by the pressure of the hydraulic fluid supplied to cylinder 146 as to maintain the amount of thrust substantially constant and thereby prevent deflection of the bed which might otherwise result from irregularities in the surfaces of the side members with which the wheels are in engagement.

As indicated above, the curing area in which the driving unit 22 is located is in the form of a kiln 12 of Quonset type construction, illustrated in FIG. 5. The kiln is normally open to the main manufacturing building 10 at its right-hand end as viewed in FIG. 1 and closed at its opposite end just beyond the end of track 20. A door 164 (FIG. 1) is provided for closing the entrance to the kiln during the curing operation, at which time steam or hot oil is circulated through a series of pipes 166 which, as shown in FIG. 5, are suitably supported beneath the stress frame of casting bed 14 between track rails 21, so as to produce the required curing temperature within the kiln. The kiln may also be provided with a plurality of unit heaters 168 supported above the casting bed at spaced intervals along the length of the kiln, and with drop-leaf dampers 170 which control the outflow of air from the kiln through openings along the base of the kiln wall. If desired, the kiln may also be provided with a plurality of roof-mounted exhaust fans 172.

In order to confine the heated curing atmosphere to the immediate vicinity of the cast plank as it rests on the pallet 84, an insulating blanket 174 of any suitable material is suspended from the roof portion of the kiln directly above the casting bed by means of an angle iron framework 176, while the space along the sides of the pallet may be closed by curtains 178 of insulating and vapor-proof material. The upper ends of curtains 178 are fixed to the angle iron framework adjacent the side edges of blanket 174, while the lower ends are fixed to longitudinally extending channel irons 180 which are heavy enough to maintain the curtains in the vertical position illustrated in the left-hand portion of FIG. 5 during the curing operation. Also connected to channel irons 180 at spaced points along the length thereof are a plurality of nylon sash cords 182, the upper ends of which are fixed to arbors 184 rotatably supported in bearings 18.6 carried by the angle iron framework 176. The arbors may be rotated in their hearings in any suitable manner, as by electric winches (not shown), so as to raise and lower the curtains 178 as desired.

Turning now to the production equipment which is stored and used in manufacturing building 10 (FIG. 1), the pallet cleaning and oiling unit 52 and the plank cutting unit or saw 56 are of substantially the same construction as the equivalent units heretofore used in connection with the fixed bed casting system disclosed in Pat. No. 3,217,375, and therefore have not been illustrated in detail herein. However, the soffit laying and rolling units 36 and 54 and the main casting machine 40 differ in some respects from the corresponding elements of Pat. No. 3,217,375, as will appear from FIGS. 1215.

As shown in FIGS. 12 and 14, the soffit laying unit 36 comprises a framework having supporting wheels 192 which are spaced to conform to the gauge of storage tracks 50 and the track formed by rails 78 of casting 'bed 14. Mounted on framework 190- is a hopper 194, the bottom end 195 of which is rectangular in cross section and of a width slightly less than the distance between the side forms 92 of the casting bed so that it may project downwardly ino the bed and deposit a soflit layer of concrete on the pallet 84 when the unit 36 is positioned at the point 34 in FIG. 1. The hopper 194 is pivotally mounted on a shaft 196 mounted on the rear cross member 197 of framework 190 and extending transversely of the framework through bearing mounts 198 fixed to the rear Wall of the hopper. The front Wall of the hopper normally rests against an L-shaped stop member 200 fixed to the front cross member 202 of the framework. With this construction, the hopper may be titled rearwardly 9 on shaft 196 and thus elevate the bottom end 195 above the level of the jacking heads of the casting bed when the sofiit laying unit 36 is moved into and out of operating position above the bed.

Projecting rearwardly from framework 190 is an auxiliary framework 204 to which are pivotally connected downwardly depending arms 206 at the lower ends of which are mounted packing wheels 208 adapted to project downwardly into the casting bed just inside the side forms 92, indicated in broken lines in FIG. 12. The framework 190 also supports an electric motor 210 and gear box 212 which may be used to positively drive one pair of the wheels 192 of the unit 36 either along the rails of storage tracks 50 when moving the unit onto and off the transfer car 60, or along the rails 78 of casting bed 14 when moving the-unit to its operating location.

The soffit rolling unit 54 illustrated in FIGS. 1214 comprises an open framework 214 having supporting wheels 216 which, like the wheels of soflit laying unit 36, are adapted to roll on the rails of the storage tracks, the transfer car and the casting bed. Extending transversely across framework 214 intermediate the ends thereof are three cross members 218 carrying pivot supports 220 to which are pivotally connected the rear ends of forwardly extending lever arms 222, Arms 222 carry intermediate their ends bearings 224 for the axles 226 of three rollers 228. Like the bottom end 195 of hopper 194 of the sofiit laying unit 36, rollers 228 are of a width only slightly less than the distance between the side forms of the casting bed, and are provided with a plurality of circumferential, laterally spaced ribs 230 which are adapted to form grooves or depressed areas 231 (see FIG. 2) in the soffit layer of concrete forming the bottom wall of the finished planks-In order to raise and hold the rollers 228 in elevated position while the rolling unit is being positioned above the casting bed, cables 232 are connected to the forward ends of lever arms 222 and extend upwardly to winches 234 mounted on the upper cross members 236 of framework 214. V

In the fixed bed system'of Pat. No. 3,217,375, the sofiit laying and rolling units are used individually during the production cycle. However, in the system of the present invention, the soffit laying unit 36 and rolling unit 54 are used conjointly. To this end, a pair of pull bars 238 and a pair of platform units 240 are provided for detachably connecting the soffit laying and rolling units together after they have been moved individually into operating position on the rails 78 0f the casting bed;

As indicated in FIGS. 12v and 13, the pull bars 238 are detachably connected at their opposite ends to sockets 242 and 244 mounted on the sofiit laying framework 190 and rolling unit framework 214, respectively, while platform units 240 are similarly connected to the frameworks 1'90 and 214 inboard of pull bars 238, but outboard of the side forms 92 of the casting bed. Each platform unit 240 consists of a pair of vertically extending support members 246 at each end of the platform which are detachably connected at their upper ends to the frameworks of the soffit laying and rolling units and at their'lower ends to longitudinally extending frame angles 248 Which support metallic grating walkways 250. When the soifit laying and rolling units are not in use, the pull bars 238 and platform units 240 are detached and stored on the rolling unit framework 214. If desired, rolling unit 54 may also'be provided with platformsZSZ, similar-to platform units 240, suspended from the rolling unit framework 214' outboard of the middle roller 228 and the space between the middle and rear rollers, as indicated in FIGS. 12 and 13.

As will be evident from the foregoing description and FIG. 1, thesoffit laying and rolling units are unconnected and stored individually on storage tracks '50 when not in use, but are moved individually and in sequence from their stored positions to their operative positions by means'of the transfer car 60.

Referring now to FIGS. 9-11, the transfer car comprises an underframe 254 formed of channel beams and supported by wheels 256 on the rails of transfer track 58 which, as previously mentioned, runs perpendicularly to, and lies in the same horizontal plane with, main track 20. Mounted on top of underframe 254 are a pair of I-beams 258 which extend transversely across the transfer car and carry on their upper surfaces a pair of angle iron rails 260 which are parallel to, and spaced the same distance apart as, the casting bed rails 78 and the rails of storage tracks 50. The transfer car underframe 254 also supports an electric motor 262 and a chain drive 264 for driving one pair of the wheels 256, and a control cabinet 266- which is mounted on a forwardly extending auxiliary platform 268 so that movements of the transfer car may be controlled directly by an operator standing on the auxiliary platform.

In order to transfer any of the manufacturing equipment, such as the sofiit laying and rolling units, from the storage tracks 50 to their operative positions above the path of the casting bed 14 as it moves along track 20, the transfer car 60 is first positioned opposite the transfer track on which the particular unit is stored, and the unit is moved either manually or by its motor driven wheels from the storage track onto the transfer car. The operator of the transfer car next moves the car and the equipment unit supported thereon forwardly until the rails 260 on the transfer car are aligned with the rails 78 of the casting bed, whereupon the casting bed is moved by one of driving units 22, 24 to a position wherein one end of the bed abuts the transfer car. The equipment unit is then moved off the transfer car onto the adjacent end of the casting bed, after which the car is moved back to the storage area on transfer track 58.

Referring again to FIGS. 12-14 in addition to FIG 1, in order to move the sofiit laying and rolling units to their operative positions, it will be understood that the transfer car transfers the rolling unit 54 first, and then the sofiit laying unit 36, so that the latter is nearer the onloading end of the casting bed. The pull bars 238 and platform units 240 are then connected to the two units, whereupon the assembled equipment is anchored in operative position by means of a pair of equipment lockdown units indicated generally at 270 in FIGS. 1, 12 and 14, located adjacent to and on opposite sides of main track 20, to the right of transfer track 58 as viewed in FIG. 1.

As shown best in FIGS. 12 and 14, each lockdown unit 270 comprises a base plate 272 on which is mounted a vertical I-beam 274 having at its upper end a laterally projecting tongue 275 to which is pivotally connected at clevis 276 fixed to one end of a hydraulic cylinder 277 extending horiozntally inwardly with respect to the main track 20. The end of piston rod 278 which projects outwardly from cylinder 277 is provided with a tongue 280 which is adapted for ready attachment to and detachment from a clevis 282 fixed to the framework 214 of the rolling unit 54.

It will be understood that each of the other equipment units, i.e., the main casting machine 40, the pallet cleaning and oiling unit 52 and the plank" cutting unit or saw 56, is also provided with clevises similar to that shown at 282 in FIG. 14 so that they, too, maybe held in proper operative position by the lockdown units 270. Furthermore, by applying hydraulic pressure to one end or the other of the cylinders 277 of the lockdown units through piping 284 (see FIG. 16), the position of the locked-down equipment may be finely adjusted without moving the unit either manually or by its own driving mechanism. This vernier type adjustment is particularly advantageous when the plank cutting unit 56 is in use because it enables the saw to be positioned at the exact point where it is desired that the cast plank be cut.

The main casting machine 40 of the system of 'the present invention depicted in FIG. 15 embodies substantially the same elements, and operates in substane tially the same Way, as the casting machine disclosed in FIGS. 6-11 of Pat. No. 3,217,375, the principal differ ence residing in the fact that casting machine 40 includes means for raising and lowering the concrete delivery means and the core molds, or slipforms as they are commonly termed, relative to the casting bed so as to prevent interference with the jacking heads of the bead while the casting machine is being moved to and from its operative position above the bed.

As shown, casting machine 40 comprises an Open framework 286 supported by wheels 288, the transverse spacing of which is the same as that of casting bed rails 78, transfer car rails 260 and the rails of storage tracks 50. Two of the front wheels 288 may be driven by a motor 287 mounted on framework 286, through a reducing gear 289 and a chain and sprocket transmission 291. Mounted on framework 286 are a forward hopper 2190 for feeding core material to three core molds or slip forms 292 through one or more flexible, vertically collapsible boots 294, and a rear hopper 296 for feeding concrete to a chute 298 which distributes the concrete on top of and along the sides of the core molds so as to form the top wall 29, side walls 31, 37 and partition webs 33, 35 of the cast plank illustrated in FIG. 2.

Each of core molds 292 has a top wall and a pair of downwardly extending side walls providing a cross-sectional shape corresponding to that of the core openings 39 of the cast plank, the bottom and rear end being open but the front end being closed by a front Wall. The core molds 292 are supported in laterally separated positions by transversely extending mounting bars 300 which are welded to the top walls of the molds and are in turn connected to a supporting frame 302. The supporting frame is suspended by a plurality of collar structures 304 from a pair of support bars 306 which extend transversely of the framework 286, the ends of bars 306 being mounted in housing 308 which are vertically slidable on guide rods 310 carried by the framework 286. Support bars 306 are generally U-shaped when viewed from the end of the casting machine, their central portions to which collar structures 304 are attached being indicated in broken lines in FIG. 15.

Supporting frame 302 also supports the lower end of concrete feed chute 298 as well as three relatively short core material chutes 312 which extend upwardly from the front ends of the core molds 2 9.2 and deliver the core material to the interiors of the core molds from the flexible feed chutes 294, and carries at its rear end a finishing screed assembly 314. Each of core material chutes 312 is provided with a horizontally movable gate 316 by which the flow of core material to the core molds 292 may be controlled.

In FIG. 15, supporting frame 302 and the other elements carried thereby, including concrete delivery chute 298 and core molds 292, are shown in their operating positions, the casting machine 40 being supported on the rails 78 of casting bed 14 with the bottom edges of the side walls of the core molds either just above, or, as indicated, digging slightly into, the sofiit layer 27 of concrete previously laid on the pallet 84 of the casting bed. In order to raise the elements carried by supporting frame 302 to a position wherein they will clear the jacking heads of the casting bed when the casting machine is being moved into and out of operating position, each of housings 308 in which the ends of support bars 306 are mounted is provided with an inverted worm gear jacking device comprising a jack screw 318 fixed to and extending upwardly from housing 308 through a worm gear housing 320 which is fixed to a horizontal, longitudinally extending jack bar 322 mounted on framework 286. The worm gear housing 320* also supports a vertically extending jack cover 324 into which the jack screw moves when elevated. Mounted on framework 286 is a reversible jack motor 326 which drives the worm gears in housings 320 through a chain and sprocket transmission 328, reducing gears 330- carried by the forward ends of jack bars 322, and jack shafts 332, 334 which interconnect the reducing gears 330 and the warm gears in housings 320. Actuation of the worm gears in one direction or the other is effective to raise or lower the jack screws 318 and thereby vary the position of supporting frame 302 and its associated elements relative to framework 286 and the casting bed.

In manufacturing cast concrete planks by use of the system disclosed herein, the following operations are performed while the casting bed '14 makes several (in the present instance, four) traverses of the manufacturing area in building 10.

Assuming that the cast plank has been cured and is resting on the casting bed, stationary in the curing area 12, the kiln door 164 is opened, the insulating curtains 178 are raised, and the core material within the plank is removed by means of suitable vacuum equipment (not shown). The prestressed strands 41 are cut at the jacking heads 88, and the pallet side forms 92 are lowered from their substantially vertical casting positions to the outwardly inclined positions indicated in broken lines in FIG. 7 by energization of the hydraulic actuating means 104, under control of the operator at console 68, whereupon the hydraulic fluid line couplings 112 are disconnected. The console operator then supplies power to the bed driving unit 22 located in the curing area so as to move the casting bed out of the kiln, to the right as viewed in FIG. 1, and stops the motion of the bed when the cast plank is positioned under the cutting unit 56 at the desired location of the first cut. In the meantime, the cutting unit has been moved onto the transfer car 60, transferred to a position in alignment with the equipment supporting rails 78 of the casting bed 14, moved onto said rails and detachably connected to the lockdown units 270. If the casting bed is not then in precise location for the cut, the console operator adjusts the position of the saw by supplying hydraulic pressure to the cylinders 277 of the lockdown units in the proper direction. After each cut, the casting bed is again moved to the right as viewed in FIG. 1, and stopped in position for the next cut. As the severed units of the plank reach the crane My 16, they are stripped or removed from the bed by a crane or other suitable device, and loaded on dollies. In the event that the core material is not removed by vacuum equipment in the curing area, it may be dumped out of the plank units in the crane bay. Alternatively, as when the plank units are to be used as wall panels, or for other purposes where insulation is important, the core material may remain in the plank.

As hereinbefore mentioned, the casting bed 14 is moved by only one of driving units 22, 24 at a time, a result which is accomplished by the provision of suitable controls at the console 68 and interlocked solenoid actuated valves in the hydraulic power unit 66. In order to transfer the casting bed drive from one of units 22, 24 to the other, the bed must be brought to rest at a position such that the ends of the bed extend into the giln 12 and the overrun building 18, respectively, past both driving units, i.e., when the bed is at the approximate midpoint of its travel. The wheels 121 of the then-active driving unit are then moved outwardly out of contact with the bed by the application of hydraulic pressure to the proper end of the associated cylinder 146. At the same time, the wheels of the other driving unit are moved into engagement with the casting bed, whereupon the bed is ready to be moved by the other unit.

After all of the plank units have been unloaded (at which time the major portion of the casting bed has moved into the overrun building 18), the direction of movement of the bed is reversed so that it travels from the unloading-overrun area toward the curing area. During this traverse, the bed is moved continuously (instead of intermittently) at a speed of from 50 to feet per minute while the pallet 84 and side forms 92 are cleaned and oiled in preparation for the casting operation. Prior to this second traverse of the casting bed, the cutting unit 56 is transferred back to the storage tracks 50 and the pallet cleaning and oiling unit 52 is moved into operating position and detachably connected to the lockdown units 270. Before the casting bed leaves the overrun area, the prestressing strands 41 are temporarily connected to the jacking head 88 at the right-hand end of the casting bed so that they trail behind the bed as it moves toward the curing area. When the casting bed has passed through the manufacturing area, the prestressing strands are disconnected from the jacking head, passed through the openings therein toward the left-hand end of the casting bed, pulled upwardly and detachably connected to suitable chucks (not shown) mounted on the right-hand end wall of the main manufacturing building 10. The pallet cleaning and oiling unit 52 is then returned to storage and the sofiit laying and rolling units 36 and 54 are transferred into position in alignment with the casting bed, moved onto the equipment supporting rails 78 at the right-hand ends thereof, and connected together by the pull bars 238- and platform units 240. The casting bed is then moved to the right until the soffit laying and rolling assembly reaches its operative position and is detachably connected to the equipment lockdown units 270 with the concrete hopper 194 beneath the concrete supply chute 32 at the point 34 in FIG. 1.

The casting bed is then again moved to the right on its third traverse of the manufacturing area, moving continuously at a speed of from 30 to 35 feet per minute, while the sofiit layer 27 of concrete is deposited on the pallet 84, reinforcing rods 43 are placed in the soflit layer manually by a workman standing on one of the walkways 250 of the platform units 240, and the soffit concrete is 3 compacted by passage of the packing wheels 208 and rollers 228 thereover. During this traverse of the casting bed, the prestressing strands 41 are reeved through the right-hand jacking head and, in efiect, pulled into the casting bed just prior to deposit of the soflit concrete. When the casting bed reaches the right-hand end of its third traverse, in the overrun area building 18, the prestressing strands are detached from the chucks on the wall of the manufacturing building, their left-hand ends are reeved through the openings in the left-hand jacking head and fixed to the latter in the usual manner, and are then tensioned from the left-hand end of the bed by means of conventional strand jacks, after the right-hand ends thereof have been fixed to the right-hand jacking head. I The sofiit laying and rolling units 36 and 54 are then disconnected and returned individually to the storage tracks and replaced by the main casting machine 40 by means of the transfer car 60, whereupon the lockdown units 270 are detachably connected tothe casting machine so as to maintain the latter in operative position with the concrete hopper 296 and core material hopper 290 beneath the concrete and core material supply chutes 32 and 4 4, respectively. The casting bed is then moved from right to left until it reaches a position wherein the left-hand end of the pallet 84, is beneath the core molds 292 of the casting machine, whereupon the core molds and concrete feed chute, 298 are lowered into the casting bed below the tops of the jacking heads by actuation of jack screws 318. The bed is then moved continuously through the maufacturing area at a speed of from 15 to 25 feet per minute while the core material and wet concrete are delivered into the casting bed on top of the soflit layer of concrete previously deposited on the pallet. When the casting bed reaches a position wherein the right-hand jacking head is closely adjacent the wet concrete hopper, motion of the bed is stopped, the core molds and concrete feed chute are raised so as to clear the jacking head, and the casting machine is returned to storage.

The casting bed is then moved to the left-hand limit of its travel in the kiln 12, whereupon the kiln door 164 is closed, the insulating curtains 178 are lowered, and the heating medium, either oil or steam, is supplied to the pipes 166 beneath the bed so as to cure the cast concrete plank on the pallet. By subjecting the cast plank to a temperature of from to 180 F., the plank may be cured to the desired release strength in approximately 14 hours or less.

Although only one specific embodiment of the system of the present invention has been described and illustrated in the accompanying drawings, it will be apparent to those skilled in the art that various changes may be made in the details of construction of the various elements of the system without departing from the inventive concept. For example, means other than the transfer car shown, such as an overhead monorail device, may be used for sequentially moving the various equipment units into and out of their operating positions, and in lieu of using insulating, vapor-proof curtains around the plank during the curing operation, the jacking heads may be provided with suitable temperature responsive devices which maintain a constant tension on the prestressed strands in spite of wide variations in the temperature to which the stands are subjected during the curing operation. It will also be understood that, in casting concrete members of forms other than that illustrated in FIG. 2, the casting equipment may be modified accordingly, and it may be unnecessary to use the soffit laying and rolling units. Reference is therefore to be had to the appended claims for a definition of the scope of the invention.

I claim:

1. A system for manufacturing cast concrete members comprising:

a manufacturing area,

an elongated curing area and an elongated unloading.

overrun area disposed on opposite sides of said manufacturing area in collinear relationship,

a track etxending substantially the full length of said curing, manufacturing and unloading-overrun areas,

an elongated casting bed movable along said track,

said casting bed including a form on which an elongated concrete member is adapted to be case,

means for moving said casting bed along said track in opposite directions between said curing area and said unloading-overrun area, and

' means disposed in said manufacturing area for casting concrete on said form while said casting bed is moved through said manufacturing area,

said casting bed remaining stationary in the curing area while the member cast on said form is cured.

2. A system for manufacturing cast concrete members as claimed in claim 1 including:

means disposed in said manufacturing area for cutting the cured concrete member on said form into individual pieces of desired lengths while said casting bed 'is moved through said manufacturing area from said curing area toward said unloading-overrun area.

3. A system for manufacturing cast concrete members as claimed in claim 1 including:

means disposed in said manufacturing area for cleaning said form preparatory to casting of said member thereon while said casting bed is moved through said manufacturing area from said unloading-overrun area toward said curing area. a 4. A system for manufacturing cast concrete members as claimed in claim 1 wherein:

' said means for moving said casting bed comprises a plurality of driving units located at spaced intervals along said track, r

each of said driving units including reversible motor means and rotatable means driven by said motor means having driving engagement with said casting bed. i

5. A system for manufacturing cast concrete member as claimed in claim 1 wherein:

said means for moving said casting bed comprises a plurality of driving units located at spaced intervals along said track, each of said driving units including a pair of variable speed, reversible hydraulic motors located on opposite sides of said track and a pair of wheels driven by said motors having frictional driving engagement with said casting bed, and means for so controlling said driving units that said casting bed is driven by only one driving unit at a time.

6. A system for manufacturing cast concrete members as claimed in claim 1 wherein:

said concrete casting means comprises means are depos iting a sofiit layer of concrete on said form while said casting bed is moved through said manufacturing area from said curing area toward said unloading-overrun area, and means for depositing on said soffit layer a body of concrete forming the remainder of said member while said casting bed is moved through said manufacturing area from said unloading-overrun area toward said curing area. 7. A system for manufacturing cast concrete members as claimed in claim 1 wherein:

said casting bed includes a pair of side members extending the full length of said bed, and a pair of rails mounted on said side members on which said concrete casting means is supported while said casting bed is moved through said manufacturing area. 8. A system for manufacturing cast concrete members as claimed in claim 7 wherein:

said means for moving said casting bed comprises a pair of driving units located adjacent said track in said curing area and said unloading-overrun area, respectively, each of said driving units including a pair of variable speed, reversible motors located on opposite sides of said track and a pair of wheels driven by said motors having frictional driving engagement with said side members of said casting bed. 9. A system for manufacturing cast concrete members as claimed in claim 8 including:

means for moving said wheels into and out of engagement with said side members. 10. A system for manufacturing cast concrete members as claimed in claim 1 wherein:

said casting bed includes a pair of longitudinally extending side forms and a cooperating pallet to shape said elongated cast concrete member, said side forms being mounted on said casting bed for pivotal movement about horizontal axes between substantially vertical positions and outwardly inclined positions, and actuating means for moving said side forms about their pivotal axes from said vertical positions to said inclined positions after said member has been cured. 11. A system for manufacturing cast concrete members as claimed in claim 1 wherein:

said casting bed includes a stress frame and vertically disposed prestressing jacking heads at the opposite ends of said form, and said concrete casting means includes concrete delivery means and core molds adapted to extend downwardly into the casting bed below the tops of said jacking heads during the casting operation, and means for elevating said concrete delivery means and core molds relative to the casting bed prior to and after the casting operation to prevent interference with 16 said jacking heads during relative movement of said casting bed and said concrete casting means. 12. A system for manufacturing cast concrete members comprising:

a manufacturing area, an elongated curing area and an elongated unloadingoverrun area disposed on opposite sides of said manufacturing area in collinear relationship. a track extending substantially the full length of said curing, manufacturing and unloading-overrun areas, an elongated casting bed movable along said track, said casting bed including a form on which an elongated concrete member is adapted to be cast, means for moving said casting bed along said track in opposite directions between said curing area and said unloading-overrun area, means for cleaning said form preparatory to casting of said member thereon, means for casting concrete on said form, means for cutting said member into individual pieces of desired length after said member has been cured and while it remains on said form, storage tracks in said manufacturing area on which said form cleaning means, concrete casting means and cutting means are stored when not in use, means for sequentially transferring said form cleaning means, concrete casting means and cutting means from said storage tracks to operating positions above said first-named track, and means for holding said form cleaning means, concrete casting means and cutting means in their respective operating positions while said casting bed is moved through said manufacturing area. 13. A system for manufacturing cast concrete members as claimed in claim 12 wherein:

said holding means is mounted at a fixed position in said manufacturing area adjacent said track and is detachably connectable to said form cleaning means, concrete casting means and cutting means, said holding means including means for varying the operating position of any of said form cleaning means, concrete casting means and cutting means relative to said casting bed. 14. A system for manufacturing cast concrete members as claimed in claim 12 wherein:

said holding means is mounted at a fixed position adjacent said track and is detachably connectable to said cutting means, said holding means including hydraulically actuated means for varying the operating position of said cutting means relative to said casting bed when said bed is stationary beneath said cutting means. 15. A system for manufacturing cast concrete members as claimed in claim 12 wherein:

said casting bed includes a pair of side members extending the full length of said bed and having a pair of rails mounted thereon on which said form cleaning means, concrete casting means and cutting means are adapted to be supported while said casting bed is moved throughv said manufacturing area, and wherein: said storage tracks are parallel to, but lie in a plane above the plane of, said first-named track, and said transferring means include a transfer track extending perpendicularly to said storage tracks in the same plane with and intersecting said first-named track, and a transfer car movable along said transfer track for receiving said form cleaning means, concrete casting means and cutting means and moving the latter sequentially from said storage tracks to said operating positions above said first-named track, said transfer car having rails on its upper surface co- 17 18 planar with said storage tracks and with said rails 3,217,375 11/1965 Kinnard 25103 X mounted on said side members of said casting bed. 3,305,907 2/1967 Baker 25-2 References Cited J. SPENCER OVERHOLSER, Primary Examiner UNITED STATES PATENTS 5 B. D. TOBOR, Assistant Examiner 3,055,073 9/ 196-2 Gerwick 25-2 X 3,139,663 7/1964 Boswell et a1 25-2 2541 3,177,552 4/1965 Kennar 25-2 X UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,523, 343 Dated August 11, 1970 Inventor(s) William E. Mitchell It is certified that error appears in the above-identified patent; and that said Letters Patent are hereby corrected as shown below:

Column 2, lines 8-9, "invention" should read --inventive--; line 37, "producing" should read --production-; line 63, "curling" should read --curing--. Column 3, line 48, "present" should read --present--. Column 4, line 16, "to" should read --top--. Column 7, line 66, "thhe" should read --the-; line 72, "hte" should read --the--. Column 10, line 52, "horiozntally" should read --horizontally-. Column 11, line 7, "head" should read --bed--. Column 12, line 58, "giln" should read --kiln--. Column 14, line 42, "case" should read -cast-. Column 15, line 16, "are should read --for-. Column 17, last line, "Kennar" should read --Roth et al.-.

SIGNED AN SEALED 015201911 Amer:

Edwudmfleldlmlr.

AnafingOifioar mm 1. 3B.

Oomlssiom or Patna" FORM PO-1050 (IO-69] USCOMM DC 503764,;

a u s GOVEIIIIIHH nnmuc OFFICE: "I! 0-306-331 

